EyeWorld Asia-Pacific September 2018 Issue

40 EWAP REFRACTIVE September 2018 A wrinkle in LASIK by Maxine Lipner EyeWorld Senior Contributing Writer Microstriae Source: Avi Wallerstein, MD The latest on clinically significant flap striae F lap striae can mar an otherwise successful LASIK procedure. Re- cent research published in the Journal of Cataract & Refrac- tive Surgery 1 pegs the true inci- dence of this at 0.79% of cases that require intervention and consid- ered risk factors and patient out- comes, according to Avi Waller- stein, MD, assistant professor of ophthalmology, McGill University, Montreal, Canada. Investigators thought that since flap striae are the most com- mon early postop LASIK complica- tion, this was important to study further. “This is part of a refractive surgeon’s day-to-day practice, so it’s important to get granular and further understand it,’” Dr. Waller- stein said. Large study pool Included in the retrospective case- controlled series were 109,403 eyes that had undergone LASIK surgery in a multi-surgeon, multicenter practice. First, investigators deter- mined the incidence and the risk factors for clinically significant post-LASIK striae, then looked at outcomes, Dr. Wallerstein noted. “For the ones that needed an inter- vention, we reported the outcomes both before we lifted the flap and irrigated and after the treatment was done,” he said. “Then we compared those to the non-striae contralateral eyes.” Dr. Wallerstein pointed out that all the surgeons included in the study received the identical training in order to work under the umbrella of this multicenter practice. This meant that identifi- cation of patients with postopera- tive striae as well as postoperative removal of this was standardized, he stressed, adding that this makes the validity of the data even stronger. New findings Investigators learned a variety of things about striae. Prior to the study, the reported striae incidence varied between 0% and 13%. “In the large database that our study looked at, the incidence is 0.79%,” Dr. Wallerstein said. “That number is a true incidence, since it comes from more than 100,000 LASIK surgeries.” Knowing this can help improve informed consent and patient care, he pointed out. One piece of new informa- tion investigators learned was that 23.5% of cases were bilateral. Dr. Wallerstein hypothesized that the reason that some patients develop bilateral striae may be an anatomi- cal predisposition and host related. When investigators consid- ered potential factors that might predispose patients to striae, they determined that preoperative spherical equivalent and total ablation depth were the most significant risks, Dr. Wallerstein re- ported. “We found that risk fit an exponential model,” he said, add- ing that the model they created could be used to derive the relative risk of developing striae as a func- tion of the patients’ preoperative spherical equivalent. “I know that a patient who’s treated for –10 D of myopia is 6.8 times more likely to develop striae than a patient who is treated for –2 D of myopia. That’s useful infor- mation for a surgeon to know to offer detailed informed consent to the patient and to plan surgical care,” he said. Investigators found that the amount of time that passed since the LASIK procedure was complet- ed was important. “Almost 10% of striae are detected in the first hour after surgery,” Dr. Wallerstein said. “That tells us we need to keep our patients around because this process of the flap not adhering completely and shifting occurs